The present invention relates to a propeller system, and more particularly to a bearing system for a pitch change system therefor.
Typical propeller pitch change systems utilize a scotch yoke type mechanism to convert linear motion of a hydraulic piston into the rotational motion of the propeller blades such that a dynamic interface is required between the propeller blade pin, roller bearing and the yoke assembly. As horsepower increases, the loads imposed on the pitch change system correspondingly increase. This increase in load necessarily requires a size increase in the pitch change components due to the high contact stresses associated with the interaction of the roller bearings with the yoke assembly. Increasing roller size to reduce the contact stress to a reasonable level eventually becomes size prohibitive with regard to maintenance and assembly. That is, blade removal would be prohibited as the roller becomes too large to pass through the hub blade retention opening.
Various pitch change systems avoid this sizing limitation by utilizing links with self-aligning spherical bearings which connect the yoke assembly with the propeller blade trunnion pin. Although effective, a somewhat complicated system with multiple linkages is required which may increase maintenance demands.
Accordingly, it is desirable to provide a pitch change system which accommodates significant horsepower, facilitates maintenance, and minimizes the pitch change system physical envelope.